With growing severe environmental pollutions in relation to plastics wastes urgent strategies are needed. One of the suitable strategies would be to take advantage of biodegradable plastics. There have been intensive studies on biodegradable plastics in the last several decades and various products have been invented and commercialized as waste bags etc.
Biodegradable films are produced by adopting polyolefines in the presence of a biopolymer such as starch which can reduce the petroleum-based polymers consumption in the production of biodegradable composites. Starch is cheap and easily accessible and it is one of the renewable sources which can be assimilated and metabolized by great number of microorganisms (bacteria, fungi and algae . . . ). Polyethylene is one of the world's main and cheapest plastic materials. Polyethylene is obtained from ethylene and it has high chemical resistance, suitable transparency as thin films and odor free and non-irritating with low water permeability in packaging industry.
U.S. Pat. No. 6,811,599 B2; describes biodegradable thermoplastics, produced by extrusion. The product includes natural polymer, plasticizer and nanoclay particles. Nanoclay particles are used as filler which play important role in improving the mechanical properties of the product. In this invention biodegradable substances are used with different degrees of substitutions, but giving low tensile strength and low permeability to water. The system is not suitable for packaging due to its solubility in water.
U.S. Pat. No. 6,228,501 B1; describes production of composites comprised of polysaccharides and clay which are used as thermal insulator or sound absorbing materials. With addition of nanoclays the impact and tensile properties of the systems are improved compared to other commercial forms. The mechanical properties of these materials are not considered suitable for packaging industry.
U.S. Pat. No. 5,461,094 A; describes the basic composite comprised of polyethylene and starch with the help of maleic anhydride as coupling agent.
WO 9,014,388 A1; describes the production of nanocomposites comprised of nanoclay and natural polymer such as corn starch with variable contents of 5 to 50%. The polymer is of synthetic type of light polyethylene and the compatibilizer is maleic anhydride